Reversible differential control valve and systems

ABSTRACT

Unequal loading of two or more fluid motor devices simultaneously imparting movement to a load, is sensed by torsional stress of a torque tube to actuate a differential valve assembly controlling flow of fluid between a pressure source and the fluid motor devices. A valve plunger actuated by the torque tube changes the flow paths within the body of the valve assembly under control of check valves to thereby compensate for unequal loading of the fluid motor devices.

United States Patent Stockwell [451 July 18, 1972 REVERSIBLEDIFFERENTIAL 3,348,810 l0/l967 Curron,.lr. ..91/17| CONTROL VALVE ANDSYSTEMS 3,364,820 l/l968 Stockwell ..91/17| [72] Inventor: Orville E.Stockwell, 536 First Ave,

Greybull, Wyo. 82426 (22] Filed: June 19, 1970 [21 Appl. No.: 47,831

{52] U.S.Cl ..9l/6,91/17l,9l/4l2 [51] Int. Cl ..F0lb25/04,F15b 15/22[58] FleldolSearch ..9l/17l,6.412

[56] References Cited Primary Examiner-Paul E. Maslousky AlmrnevClarence A. O'Brien and Harvey B. Jacobson [57] ABSTRACT Unequalloading of two or more fluid motor devices simultaneously impartingmovement to a load. is sensed by torsional stress of a torque tube toactuate a differential valve assembly controlling flow of fluid betweena pressure source and the fluid motor devices. A valve plunger actuatedby the torque tube changes the flow paths within the body of the valveassembly under control of check valves to thereby compensate for unequalloading of the fluid motor devices.

22 Claims, 13 Drawing Figures PATENIED Jun 8 I972 SHEET 1 BF 4 OrvilleE. Sloc/r well I.\'I'E.\'TOR C BY M4016.

REVERSIBLE DIFFERENTIAL CONTROL VALVE AND SYSTEMS This invention relatesto fluid power motor systems and more particularly to systems havingdifferential load sensing and compensating means regulating movement ofloads such as elevating platforms, truck dump bodies, tractor mountedloaders, bulldozers, etc.

Fluid control systems for operating a plurality of fluid motor devicessuch as hydraulic jacks or piston devices, are well known. In suchsystems, the load is connected to a plurality of the hydraulic jacks sothat some synchronization is required in order to avoid tilting,twisting or other distortion of the load lifting member or the frame. Inorder to cope with this problem relatively complex synchronizing valvesand valve systems are utilized. In spite thereof, such fluidsynchronizing systems are often inadequate under all operatingconditions. Further, special and different valving is required fordifferent loading arrangements making the fluid system expensive andcostly to repair.

It is therefore an important object of the present invention to providea sensitive difierential control valve assembly capable of beingeconomically manufactured and utilized in different fluid load sensingsystems to compensate for unequal loading of fluid motors. A furtherobject is to provide differential load sensing means for differentloading arrangements to be used with the differential control valveassembly.

In accordance with the present invention, fluid under pressure from asuitable source is supplied to a plurality of fluid operated motors,piston devices or hydraulic jacks through a differential control valveassembly that is mechanically actuated by a sensing arrangement inresponse to tilting, twisting or any undesired distortion of a loadmember being moved. The valve assembly includes a valve plunger actuatedby the sensing system by means of which fluid flow paths within thevalve body of the valve assembly are changed under control of a systemof check valves in order to provide the desired compensating action.This differential control over the fluid operated devices is exercisedby the control valve assembly during movement of the load member ineither direction.

These, together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike nu merals refer to like parts throughout, and in which:

FIG. 1 is a perspective view showing a rear dump hoist installation fora fluid control system in accordance with the present invention.

FIG. 2 is a bottom plan view of the installation shown in FIG. I.

FIG. 3 is an enlarged partial sectional view taken substantially througha plane indicated by section line 3-3 in FIG. 2.

FIG. 4 is a sectional view through one form of reversible differentialcontrol valve assembly adapted to be utilized in the system illustratedin FIGS. 1-3.

FIG. 5 is a sectional view through a second form of reversibledifferential control valve assembly.

FIG. 6 is a sectional view through a third form of reversibledifferential control valve assembly.

FIG. 7 is a sectional view through a fourth form of reversibledifferential control valve asembly.

FIG. 8 is a sectional view through a fifth form of reversibledifi'erential control valve assembly in accordance with the presentinvention.

FIG. 9 is a perspective view showing a fluid control system for anelevating platform type of installation.

FIG. 10 is a perspective view showing yet another fluid control systemfor a tractor mounted loader installation.

FIG. 11 is a simplified, fluid circuit diagram including the hydraulicreversible difi'erential control valve assembly of the presentinvention.

FIG. 12 is a partial top plan view with parts shown in section of a sidehoist installation for the invention.

FIG. 13 is a side elevational view of the installation shown in FIG. l2.

Referring now to the drawings in detail, FIG. 11 shows a simplifiedfluid circuit with which a reversible differential control valveassembly 10 is associated in accordance with the present invention. Asingle fluid supply port associated with the reversible differentialcontrol valve assembly [0 is connected by fluid line 12 to a source offluid under pressure through a selectively controlled directionalcontrol valve of any standard type 14. The pressure source may comprisea pump 16 having a fluid pressue output 18 connected to the directionalcontrol valve 14 and an intake 20 through which fluid is withdrawn froma fluid reservoir 22 to which the directional control valve 14 is alsoconnected by the exhaust line 24. Thus, in one position of thedirectional control valve 14 as shown in FIG. 11, fluid under pressureis supplied through line 12 and the reversible differential controlvalve assembly 10 to a plurality of fluid operated devices, fluid motorsor hydraulic jacks 26. In the illustrated embodiment, a pair of singleaction piston jacks 26 are shown connected to the load ports of thereversible differential control valve assembly 10 by fluid lines 28.Thus, in the position of the directional control valve 14 as shown inFIG. 11, fluid under pressure will be supplied to the hydraulic jacks 26to cause extension of the piston rods therefrom. When the directionalcontrol valve 14 is displaced to its other operative position, fluidwill be exhausted from the hydraulic jacks so as to cause retraction ofthe piston rods. Ordinarily, fluid flow to and from both hydraulic jacksis equal. However, because of unequal loading of the hydraulic jacks,there is a tendency for the jacks to undergo movement by differentamounts or at different rates. This differential movement or unevencondition of the jacks is sensed by means to be described hereafter,thereby causing shift of a valve plunger 30 of the valve assembly 10from a neutral position. When the valve plunger 30 is in a neutralposition, bidirectional flow between all ports is permitted. When thevalve plunger is shifted from its neutral position in either direction,reflecting an uneven condition, throttling and gradual cut-off of flowto one of the hydraulic jacks occurs as one compensating action whileunidirectional cross-flow between the jacks is permitted in order tofurther compensate for the uneven condition. When the jacks areequalized as a result of this compensating action, the valve plunger 30is restored to its neutral position. The foregoing action of the valveassembly 10 occurs regardless of the direction in which flow isconducted through the fluid line 12. Similar load compensating actionmay be applied to a fluid control system for double action piston jacksutilizing the difierential control valve assembly 10 as will behereafter discussed in greater detail.

FIG. 4 illustrates one embodiment of the differential control valveassembly 10. The valve assembly includes a valve body 32 within whichthe valve plunger 30 is slidably mounted. The valve plunger includes endland portions 34 which project through the ends 36 and 38 of the valvebody in wiping engagement with the seals 40. The land portions 34 of thevalve plunger are internally threaded for threaded reception of aconnector 42 at one end of the valve plunger through which the sensingsystem may impart movement to the valve plunger 30 in either directionfrom the neutral position shown in FIG. 4. In the illustratedembodiment, the valve plunger 30 is also provided with an intermediateland 44 spaced from the end portions 34 by smaller diameter spoolportions 46.

The valve body is provided with a pair of load ports 48 respectivelyconnected by fluid lines to the fluid operated devices as aforementionedin connection with FIG. 11. The ports 48 are disposed on the side 50 ofthe valve body 32 opposite the side 52 through which a single supplyport 54 extends for connection to the source of fluid. The load ports 48establish communication with spaced valve cavities formed by the bore 56through which the valve plunger 30 is slidably shifted. The valvecavities are disposed about the small diameter spool portions 46 of thevalve plunger and each valve cavity extends axially between a pair ofparallel passages or conduits 58 and 60 formed in the valve body incommunication with the valve cavities in bore 56. Fluid communication isestablished between the parallel passages 58 and 60 and the control port54 through connecting passage 62 and two pair of pressure responsivecheck valve assemblies 64 and 66 associated with the passages 58 and 60on either side of the supply port 54.

The connecting passage 62 intersects valve chambers 68 on either side ofthe port 54 associated with the check valve assemblies 66. The valvechambers 68 are closed and sealed at the side 52 of the valve body bythe threaded plugs 70 having pins 72 projecting into the valve chamberfor positioning springs 74 biasing check elements 76 to the closedpositions shown blocking flow in one direction through the associatedpassages 60. The check valve assemblies 64 on the other hand associatedwith the passages 58, include valve chambers 78 seating ball checkelements 80 for blocking flow in one direction between the passages 58and the connecting passage 62 under the bias of springs 82 positioned onthe threaded plugs 84 sealing the valve chambers at the ends 36 and 38of the valve body. Thus, the check valve assemblies 64 and 66 block flowthrough the associated passages 58 and 60 in opposite directions.

With the valve plunger 30 in the neutral position illustrated in FIG. 4,fluid flow under pressure from the supply port 54 will be conductedthrough connecting passage 62 and past the check valves 64 to both loadports 48 through passages 58 and valve cavities 56 surrounding the spoolportions 46 of the valve plunger 30. Fluid flow in the other directionfrom the load ports 48 to the supply port 54 on the other hand, will beconducted along parallel paths which include the passages 60 past thecheck valves 66. Further, fluid flow may be conducted between the loadports 48 in the neutral position of the valve plunger 30. Thus, flow inboth directions between all three ports 48 and S4 is accommodated,requiring only enough pressure to open the check valves against the biasof the associated springs.

In response to an uneven condition of the hydraulic jacks in the fluidsystem with which the reversible differential control valve assembly Iis associated, the valve plunger 30 will be axially shified in onedirection or the other from its neutral position. The intermediate land44 of the valve plunger will then block fluid communication between oneof the load ports 48 and associated passage 60 while fluid communicationbetween the other load port and the associated passage 58 will beblocked by one of the end land portions 34 of the valve plunger.Consider, for example, that the valve plunger 30 is shifted in a lefthand direction as viewed in FIG. 4 to one of its load compensatingpositions wherein the stop head 86 abuts the end 38 of the valve body.The intermediate land 44 of the valve plunger will then block flowbetween the left hand port 48 and passage 60 as viewed in FIG. 4 whilethe right hand end portion 34 of the valve plunger will block flowbetween the right hand port 48 and right hand passage 58. Flow in onedirection may then be conducted between the supply port 54 and the lefthand load port 48 past check valve 64 in order to extend the piston rodof the hydraulic jack to which the lefl hand port 48 is connected forequalizing purposes. Fluid flow in the other direction will be conductedbetween the right hand load port 48 and the supply port 54 past theright hand check valve assembly 66 in order to permit retraction of thehydraulic jack connected to the right hand load port 48. Also, fluidcross-over flow may be conducted in one direction only from the righthand port 48 to the left hand port past the right hand check valve 66and the lefi hand check valve 64. A reversal in flow direction betweenports from that described can occur if the valve plunger 30 is shifiedto its other load compensating position with the stop head 88 abuttingthe end 36 of the valve body.

The reversible differential control valve assembly 10' illustrated inFIG. is basically the same as the valve assembly shown in FIG. 4 exceptfor a reversal in position of the supply and load ports. Thus, thesupply port 54' communicates with the valve bore 56' through connectingpassage 62'. The valve plunger 30' controls fluid communication betweenthe connecting passage 62' and two pair of parallel conduit portions orpassages 58' and 60'. A check valve assembly 64' is associated with eachpassage 58 while a check valve assembly 66' is associated with eachpassage 60'. The structure and action associated with the valve plunger30' andthe check valve assemblies 64 and 66' are substantially the sameas described in connection with the valve plunger 30 and check valveassemblies 64 and 66 of the valve assembly 10, except that the checkvalve assemblies 66' are associated with load port fittings 90threadedly mounted in the valve body 32'. The fittings 90 are formedwith axial passages 92 constituting the load ports in fluidcommunication with the valve chambers 68' associated with the checkvalve assemblies 66. Thus, the valve assembly I0 performs all of thefunctions described in connection with the valve assembly 10 in asimilar manner.

The reversible differential control valve assembly 94 illustrated inFIG. 6, also performs the same functions described in connection withthe reversible differential control valve assembly I0 illustrated inFIG. 4. This valve assembly includes a valve body 96 provided with avalve bore 98 through which a valve plunger 100 is axially shifted inorder to differentially control flow of fluid to and from the load ports102 in communication with the valve bore on a side of the valve bodyopposite the side through which a supply port I04 extends within anexternally threaded fitting I06. The axial end portions 108 of the valveplunger 100 when displaced from the neutral position illustrated in FIG.6, block one of the two parallel passages I10 in order to interruptfluid communication with one of the load ports 102. An intermediate landportion 112 on the valve plunger when axially shifled in eitherdirection from the neutral position illustrated, interrupts fluidcommunication between one of the load ports and a common passage II4 inthe valve body as well as to block bidirectional crossflow between theports I02 through the cavity 115.

A pair of oppositely directed check valve assemblies 116 control fluidflow between the passages IIO and a connecting passage 118 intersectingthe valve chamber 120 associated with check valve assembly 122 which isbiased by spring I24 to a seated position as illustrated in FIG. 6blocking flow in one direction between the common passage I14 and thesupply port I04 in communication with the valve chamber 120. The spring124 is positioned within the valve chamber by a projection I26 on thefitting I06. The valve assembly 94 is hence similar to the valveassembly I0 of FIG. 4, except that the two passages 60 are replaced bythe common passage I I4 while the two check valve assemblies 66associated with the passages 60 are replaced by a single check valveassembly 122.

A further reduction in the number of parts associated with thereversible difierential control valve assembly is exemplified by thevalve assembly I28 illustrated in FIG. 7 wherein a pair of load portsI30 are disposed on one side of the valve body 132 opposite the sidethrough which the supply port I34 extens, as in the other valveassemblies. The load ports I30 communicate with the valve bore 136within which the valve plunger 138 is movable while the supply port 134is in communication with the valve chamber of a check valve assembly140, as in the case of the valve assembly 94. However, the twooppositely directed check valve assemblies 116 as described inconnection with FIG. 6, are replaced by a single check valve assemblyI40 and the valve chamber I46 of check valve assembly 142. The checkvalve assembly 142 is biased to its closed position by a spring seatedon a projection extending from a threaded plug I48 closing the valvechamber I46 with which a pair of passages I54 and I52 are incommunication. The passages I52 and I54 conduct flow of fluid betweenthe valve chamber 146 and the valve cavities in valve bore I36 axiallyspaced by the intermediate land 155 of the valve plunger 138. Also, apassage I56 conducts flow of fluid between the valve chamber of checkvalve assembly and the right hand valve cavity of valve bore 136 as seenin FIG. 7.

The valve plunger I38 is similar in external shape to the valve plungersassociated with the previously described valve assemblies. However, thevalve plunger [38 is provided with an internal bore passage 158 closedat opposite axial ends by threaded plugs associated with the stopelements 160 and 162. Fluid communication is established between theinternal passage 158 and the two outboard axially spaced valve cavitiesof valve bore 136 by means of a plurality of circumferentially spacedopenings 164 extending through the axial end portions 166 of the valveplunger. A flow path is thereby established between the load ports inthe neutral position of the valve plunger 138 as in the case of thevalve assembly 94 illustrated in FIG. 6.

It will be apparent that the reversible differential control valveassembly 128 illustrated in FIG. 7 in addition to utilin'ng a commonpassage 56 through which flow toward the supply port 134 is conducted asin the case of valve asembly 94, replaces the two oppositely directedcheck valve assembly 116 of the valve assembly 94 with a single checkvalve assembly 142, through which flow is conducted from the supply port134 to both of the load ports 130 via conduits 152 and 154 when thevalve plunger 138 is in the neutral position illus trated. Axial shiftof the valve plunger to one load compensating position or the other,will cause its land 155 to block flow through one of the passages 152and 154 to one of the load ports 130 while cross-flow in one directionpast check valve 140 will be conducted from the blocked port 130 to saidone load port. Bi-directional cross-flow between the load ports 130 isconducted through the internal passage 158 in the valve plunger and theopenings 164 in the neutral position of the valve plunger.

A further structural simplification is effected with respect to thevalve body 168 of the reversible differential control valve assembly 170illustrated in FIG. 8. The valve body 168 is provided with a pair ofload ports 172 on one side thereof opposite the side provided with thesingle supply port 174 as in the case of the valve body 32' of the valveassembly illustrated in H6. 5. The load ports 172 are in fluidcommunication with the valve bore I76 cooperating with a valve plunger178 as in the case of the valve assembly 94 illustrated in FIG. 6 sothat bi-directional cross-flow is established between the load ports inthe neutral position of the valve plunger. In the neutral position ofthe valve plunger I78, fluid communication is also established betweenboth of the load ports 172 and th supply port 174 through a connectingpassage 180 and valve cavities 182 adjacent the opposite axial ends ofthe valve plunger and a valve cavity 184 intermediate the other twovalve cavities 182. Thus, bi-directional cross-flow may occur betweenthe ports in the neutral position of the valve plunger 178 without anyopening of check valves as in the case of the valve assembliesillustrated in FIGS. 6 and 7.

The reversible differential control valve assembly 170 features a pairof oppositely directed check valve assemblies [86 mounted within thevalve plunger I78 itself. Accordingly, the valve plunger is providedwith axially spaced bores 188 at the opposite axial ends thereof closedby the externally threaded plug portions I90 associated with the stopelements 192 and 194. The plugs are provided with retainer sockets atthe inner ends thereof seating springs I94 biasing the check valveelements 196 to closed positions seated at the ends of small diameterpassages 198 within the valve plunger. The inner ends of the passages198 are spaced from each other by the solid intermediate land portion200 of the valve plunger. The passage 198 is in communication with thevalve bore I76 through openings 202. it will be apparent therefore, thatupon axial shift of the valve plunger 178 to one of its loadcompensating positions, flow of fluid in one direction from the supplyport 174 to one of the load ports will be blocked by one of the checkvalve assemblies 186 within a valve cavity 182 at one axial end of thevalve plunger while flow to the other load port will be conductedthrough the valve cavity 184, openings 202, one of the passages 198 pastone of the check valve elements I96 and one of the valve cavities 204 tothe other load port. Flow past the opened check valve element 196 intothe valve cavity 204 is conducted through openings 206 disposed betweenthe valve land portions 208 and 210 on both sides of the intermediateland portion 200. While flow of fluid in one direction from the supplyport 174 to one of the load ports I72 is blocked by a check valveassembly I86, flow in the opposite direction from this port 172 to theport 174 is accommodated through an associated valve cavity 204,openings 202, passage 198 past the check valve element 196, openings206, valve cavity 182 and connecting passage 180. Flow from this loadport to the other load port is also accommodated at the same timethrough the valve space 184.

Because of the foregoing construction and operation of the refersibledifferential control valve assemblies, relying on the action of checkvalves to control flow along different paths for load equalizationpurposes in response to shift of the single valve plunger, a relativelyshort stroke is all that is needed in connection with the movement ofthe valve plunger. In view thereof, amplifying linkages are not requiredto transmit differential information to the valve assembly through theconnector 42 associated with the valve plunger as described inconnection with FIG. 4. The reversible differential control valveassemblies hereinbefore described are therefor ideally suitable tovarious installations through which differential load information iscollected and delivered to the reversible differential contro valveassembly, with different levels of sensitivity. The reversibledifferential control valve assembly is therefore applicable to manydifferent installations such as machine tools, elevating platforms,material handling equipment, side hoise and rear dump bodies on truckvehicles and earth moving equipment.

FIGS. 1, 2 and 3 illustrate a rear dump truck installation generallyreferred to by reference numeral 212. ln this installation, a loadmember such as the floorboard 214 of a dump body carried on parallelspaced, beams 216, is pivotally displaced relative to the chassis frameof the vehicle to which the piston rods associated with hydraulic jackcylinder portions 218 are connected. The cylinder portions 218 arepivotally connected to the platform or load frame assembly 2l6-2l4 attwo transversely separated points by bearing assemblies secured to theload frame structure. Fluid under pressure is supplied to the cylinderportions by fluid lines 224 and 226 for pivotally elevating the loadmember by extension of the piston rods associated with the hydraulicjacks. Lowering of the load member on the other hand is accommodated byexhaust of fluid from the cylinder portions through the fluid lines 224and 226. Fluid under pressure is supplied to and exhausted from thelines 224 and 226 through a reversible differential control valveassembly 10 for example, the valve body of which is foredly mounted on amounting bracket 228. The mounting bracket 228 is fixed to a cross-beam230 interconnecting the parallel spaced beams 216. The valve assembly 10is thereby fixedly mounted on the load member in a position forconducting fluid under pressure to and from the cylinder portions 218through lines 224 and 226. Fluid from a suitable source is supplied tothe reversible different control valve assembly 10 by the fluid line 232in order to effect raising and lowering of the load through the cylinderportions 218 of the hydraulic jacks as hereinbefore described inconnection with FIG. ll. The control valve assembly l0 as hereinbeforeexplained acts to differentially restrict cylinder travel when its valveplunger is actuated in one direction or another from the neutralposition by a sensing device generally referred to by reference numeral234.

The sensing device 234 includes a torque tube 236 that is disposedgenerally parallel to the beams 216. An actuating arm 238 is rigidlyconnected to one axial end of the torque tube while an anchoring arm 240is rigidly secured to the other axial end. The anchoring arm 240 isfixed to the load member in an angularly adjustable position by abracket 242 and a fastener assembly 244, the bracket being secured to across member 246 of the load frame. The end of the torque tube oppositethe anchoring arm 240 is pivotally mounted by the bearing 248 onmounting bracket 228 about the longitudinal axis of the torque tube.

It will be appreciated that any bending of the load member or distortionthereof during movement by the hydraulic jacks will result in twist orangular displacement of the plane defined by the locations at which thecylinder portions of the hydraulic jacks are connected to the loadmember. This will result in relative angular displacement betweenlongitudinally spaced portions of the load member along the longitudinalaxis of the torque tube 236. Thus, since the torque tube is anchored atone axial end by the anchor arm 240 to the load member and is pivotallymounted by the bracket 228 at its other axial end, by means of the pivotassembly 248, there will be some angular displacement of the arm 238secured to the non-anchored end of the torque tube pivotally mounted onthe load member. The amount of angular displacement of arm 238 or thesensitivity of the sensing device 234 may be varied by changing theaxial length of the torque tube and the longitudinal spacing of thelocations at which the axial ends of the torque tube are respectivelyanchored. The actuating arm 238 angularly displaced in response totorsional twist of the torque tube will accordingly cause shifting ofthe valve plunger of the valve assembly engaged by the actuating flange250 projecting from the actuating am 238 and connected to the valveplunger connector.

The torque tube sensing arrangement described in connection with FIGS.1, 2 and 3 will also be useful in connection with a side hoistinstallation as shown in FIGS. 12 and i3 wherein a torque tube 252 ispivotally mounted on a frame 254 by means of a pair of journal brackets256 pivotally supported control lever arms 260 and 262 adjacent oppositeaxial ends of the torque tube 242, these lever arms being connected bylinks to the load member such as the side hoist body adapted to bepivotally displaced by the hydraulic jacks to which fluid under pressureis supplied to and exhausted from by a pair of flexible hose 264extending from one side of the reversible differential control valveassembly 10, the hose 266 extending from the other side being connectedto the source of fluid under pressure as aforementioned. The valveassembly 10 in this installation is secured to the control arm 260 forpivotal movement with torque tube 252. When even load conditions exist,both control arms 260 and 262 will be displaced by the same amount.Differential displacement of the control arms 260 and 262 will howeveroccur as a result of any uneven condition to cause actuation of thevalve plunger of valve assembly 10. Thus, the axial end of the torquetube 252 adjacent the control arm 262 is anchored in an adjustedposition to the control arm 262 by means of an anchoring arm 268 havingan adjustment slot 270 through which the bolt 272 extends in threadedengagement with a nut 274 welded to the control arm 262. The other axialend of the torque tube 252 is rigidly connected to an actuating arm 276having an actuating projection 278 connected to the valve plunger of thereversible differential control valve assembly 10.

It will be apparent from the foregoing description of FIGS. l, 2 and 3on the one hand and the description of FIGS. 1 1 and 12 on the otherhand, that different types of unequal loading may be sensed byappropriate sensing devices to supply information to the differentialcontrol valve assembly in order to produce its compensating actionthrough difierential control of 2 or more hydraulic jacks. In FIG. 9, amore complex system is illustrated wherein four corner jacks 280anchored to a frame 282 support an elevating platform 284. Fluid underpressure is supplied to the hydraulic jacks 280 from a pressure sourceconsisting of the pump 286 and a fluid reservoir 288. Fluid underpressure from the pump is routed to a supply line 290 through adirectional control valve 292 in one position thereof while fluid underpressure is supplied to a second fluid line 294 in the other operativeposition of the directional control valve. Fluid is exhausted from oneof the supply lines 290 and 294 through the return line 296. Thus, thehydraulic jacks 280 are of the two-way acting type with fluid beingeither supplied under pressure or exhausted from the opposite ends ofthe cylinder portions of the hydraulic jacks.

la the installation illustrated in FIG. 9, three difi'erential controlvalve assemblies are utilized in association with three load sensingtorque tubes 298 and 300 and 301. The fluid line 290 is directlyconnected to the upper ends of each of the four hydraulic jacks 280while line 294 is connected to the supply port of valve assembly 10. Thelower ends of two of the hydraulic jacks are connected to the load portsof difi'erential control valve assemblies 10'. The supply port of valveassembly I0 is connected by line 301 to the one of the load ports of thedifferential control valve assembly 10. Similarly the lower ends of theother two jacks 280 are connected to the load ports of reversibledifferential control valve assembly 10" having a supply port connectedto the other load port of the valve assemblies 10 and 10" arerespectively associated with the torque tubes 300 and 298 ininstallational arrangements similar to that described with respect toFIGS. 11 and 12. For example, the control valve assembly 10' is mountedon a control arm 302 connected by link 304 to the platform 284. Thecontrol arm 302 is pivotally mounted on the frame by the bracket 306 forpivotal displacement about an axis on which the torque tube 300 ispivotally mounted. The end of the torque tube 300 adjacent the valveassembly 10' is provided with an actuating arm as hereinbefore describedin connected with FIGS. 11 and 12 while the other end of the torque tube300 is connected to the other control arm 306 which is in turn connectedby the link 308 to the platform 284 in laterally spaced relation to thelocation at which the link 304 is connected. Thus, during lowering orelevating of the platform, if any lateral tilt of the platform occurs,this will be reflected by torsional twist of the torque tube 300 therebyactuating the control valve assembly 10' producing its compensatingaction on the hydraulic jacks in order to restore the platform to alevel condition. The lateral tilt of the platform adjacent one end issensed by means of the torque tube 300 while lateral tilt at theopposite end will be sensed by the torque tube 298 operating through thevalve assembly 10" in a similar fashion in order to provide acompensating effect on the operation of the associated hydraulic jacksat that end of the platform. Tilt of the platform in a directionperpendicular to the lateral tilt sensed by the torque tubes 300 and298, will be sensed by a third torque tube 301 arm, link and valveassembly 10, transversely located relative to the other two. Thus,longitudinal tilt of the platform may be compensated for through theeffect of control valve assembly 10 on each of the hydraulic jacks towhich it is connected in series with one of the other two valveassemblies 10' and 10".

FIG. 10 illustrates a tractor mounted loader installation in which aload bucket 316 is pivotally connected through a pivot rod 318 to theouter ends of a pair of laterally spaced positioning lever arms 320,having slots 322 through which the cylinder portions 324 of hydraulicjacks extend. Pins 326 pivotally connect the cylinder portions of thehydraulic jacks to the arms 320 so that the bucket 316 may be raised andlowered by simultaneous upward and downward pivotal displacement of thearms 320. Pivotal movement is imparted to the arms 320 by extension orretraction of the piston rods relative to the cylinder portions 324.Fluid under pressure is accordingly supplied to or exhausted from theupper ends of the cylinder portions through a pair of fluid lines 328extending from the reversible differential control valve assembly 10connected by the fluid line 330 to the source of fluid.

The valve body of the valve assembly 10 is fixedly secured to one of thearms 320. This same arm, fixedly mounts a hearing bracket 332 joumalingone end of a torque tube 334 having an actuating arm 336 fixedly securedthereto. The other end of the torque tube had an anchor arm 338 fixedthereto, the anchor arm being fixedly mounted in an adjusted position tothe other arm 320 opposite the arm on which the valve assembly 10 ismounted. Thus, any relative movement between the two anns 320 will besensed by torsional strain of the torque tube 334 thereby actuating thevalve assembly 10 through the actuating arm 336 as hereinbeforedescribed in connection with the other installations.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

I. ln combination with a source of fluid and a plurality of fluidoperated devices, load means connected to said fluid operated devices,sensing means connected to the load means and valve means actuated bysaid sensing means for differential controlling flow of fluid inopposite directions between the source and the fluid operated devices toequalize movement thereof said valve means including a valve body, avalve element displaceable by the sensing means from a neutral positionto compensating positions in which flow is blocked between the sourceand one of the fluid operated devices, passage means in the valve bodyconducting fluid through different flow paths intersected by the valveelement to differentially restrict flow in response to actuation by thesensing means and unidirectional flow blocking means mounted in saidpassage means for selecting the flow paths through which fluid isconducted in response to displacement of the valve element from saidneutral position whereby cross flow between the fluid operated devicesoccurs to enhance equalizing movement.

2. The combination of claim 1 wherein said passage means includes a pairof load ports connected to the fluid operated devices, a supply port andparallel flow conduit portions respectively conducting flow in oppositedirections between the supply port and each of the load ports, and adirectional control valve connecting the supply port to the source offluid.

3. The combination of claim 2 wherein said flow blocking means includespressure responsive check valves blocking flow in opposite directionsthrough said parallel conduit portions.

4. The combination of claim 3 wherein flow to and from each of the loadports is respectively conducted by two of the parallel conduit portions.

5. The combination of claim 3 wherein flow in one direction is conductedthrough only one of the parallel conduit portions.

6. The combination of claim 5 wherein a single one of the check valvesblocks flow through two of said parallel conduit portions.

7. The combination of claim 6 wherein said check valves are mountedwithin the valve element.

8. The combination of claim 3 wherein a single one of the check valvesblocks flow through two of said parallel conduit portions.

9. The combination of claim 3 wherein said check valves are mountedwithin the valve element.

10. The combination of claim 1 wherein said sensing means includes anelongated torque tube, anchoring means connecting the torque tube at oneend to the load means, and actuating means connected to the other end ofthe torque tube for engagement with the valve element.

11. The combination of claim 10 wherein the load means comprises aframe, a movable member pivotally mounted on the frame and meansconnecting the fluid operated devices to the member.

12. The combination of claim ll including bracket means fixedly mountingthe valve body on the member and pivotally mounting the torque tubeadjacent thereto at said other end, said one end of the torque tubebeing fixedly anchored by the anchoring means to the member, said torquetube extending transversely between the fluid operated devices.

13. The combination of claim ll wherein said connecting means comprisesa pair of operating lever arms.

14. The combination of claim 13 including bracket means fixedly mountingthe valve body on one of the lever arms and pivotally mounting thetorque tube adjacent thereto at said other end said one end of thetorque tube beinfilfixedly anchored by the anchoring means to the otherof e lever arms.

15. The combination of claim 1 wherein the load means includes a frameto which the fluid operated devices are anchored, and a platformsupported by the fluid operated devices.

16. The combination of claim 15 wherein said sensing means includesactuating means pivotally mounted on the frame and engageable with thevalve for detecting movement of the platform.

17. The combination of claim 16 including additional valve meansinterconnecting with the source of fluid through said first mentionedvalve means for detecting unequal displacement of the platform by thefluid operated devices.

18. The combination of claim 17 including an elongated torque tubepivotally mounted by the frame at opposite ends, link means connectingthe torque tube at said ends to the platform, the valve elementassociated with said additional valve means being engageable by the linkmeans at one of said ends of the torque tube.

19. in combination, a frame, a load member movably mounted on the frame,a plurality of fluid operated devices anchored to the frame, meansinterconnecting the load member with the fluid operated devices atspaced locations, a source of fluid under pressure, directional controlmeans con necting the source to the fluid operated devices for impartingmovement to the load member in opposite directions, means connected tothe load member for sensing unequal movement of the fluid operateddevices during movement of the load member, valve means connected tosaid fluid operated device for differentially restricting flow betweenthe directional control means and the fluid operated devices in responseto engagement by the sensing means to compensate for said unequalloading, passage means connected to the valve means for conducting saidflow in opposite directions along different flow paths, andunidirectional flow blocking means responsive to said unequal movementof the fluid operated devices for conducting cross flow therebetweenalong selected ones of said flow paths.

20. The combination of claim 19 wherein said sensing means includes atorque tube connected to the load member, and actuating meansdisplaceable by the torque tube into engagement with the valve means.

21. The combination of claim 19 wherein said valve means includes avalve body, a valve element displaceable by the sensing means from aneutral position to compensating positions blocking flow between thedirectional control means and one of the fluid operated devices.

22. ln combination with a pair of fluid operated devices, a source ofworking fluid and means for sensing unequal loading of the fluidoperated devices, a control valve assembly comprising a valve blockhaving a pair of load ports connected to said fluid operated devices anda supply port connected to said source, a single valve element connectedto the sensing means, means mounting the valve element within the valveblock for displacement from a neutral position by the sensing means todifferentially restrict flow of the working fluid between the supplyport and said pair of load ports, passage means mounted within the valveblock for conducting flow of the working fluid in opposite directionsbetween the supply and load ports along separate and different flowpaths, and pressure responsive check valve means mounted in the passagemeans for unidirectionally conducting cross flow between said load portsin response to unequal loading of the fluid operated devices.

t i l i i

1. In combination with a source of fluid and a plurality of fluidoperated devices, load means connected to said fluid operated devices,sensing means connected to the load means and valve means actuated bysaid sensing means for differential controlling flow of fluid inopposite directions between the source and the fluid operated devices toequalize movement thereof said valve means including a valve body, avalve element displaceable by the sensing means from a neutral positionto compensating positions in which flow is blocked between the sourceand one of the fluid operated devices, passage means in the valve bodyconducting fluid through different flow paths intersected by the valveelement to differentially restrict flow in response to actuation by thesensing means and unidirectional flow blocking means mounted in saidpassage means for selecting the flow paths through which fluid isconducted in response to displacement of the valve element from saidneutral position whereby cross flow between the fluid operated devicesoccurs to enhance equalizing movement.
 2. The combination of claim 1wherein said passage means includes a pair of load ports connected tothe fluid operated devices, a supply port and parallel flow conduitportions respectively conducting flow in opposite directions between thesupply port and each of the load ports, and a directional control valveconnecting the supply port to the source of fluid.
 3. The combination ofclaim 2 wherein said flow blocking means includes pressure responsivecheck valves blocking flow in opposite directions through said parallelconduit portions.
 4. The combination of claim 3 wherein flow to and fromeach of the load ports is respectively conducted by two of the parallelconduit portions.
 5. The combination of claim 3 wherein flow in onedirection is conducted through only one of the parallel conduitportions.
 6. The combination of claim 5 wherein a single one of thecheck valves blocks flow through two of said parallel conduit portions.7. The combination of claim 6 wherein said check valves are mountedwithin the valve element.
 8. The combination of claim 3 wherein a singleone of the check valves blocks flow through two of said parallel conduitportions.
 9. The combination of claim 3 wherein said check valves aremounted within the valve element.
 10. The combination of claim 1 whereinsaid sensing means includes an elongated torque tube, anchoring meansconnecting the torque tube at one end to the load means, and actuatingmeans connected to the other end of the torque tube for engagement withthe valve element.
 11. The combination of claim 10 wherein the loadmeans comprises a frame, a movable member pivotally mounted on the frameand means connecting the fluid operated devices to the member.
 12. Thecombination of claim 11 including bracket means fixedly mounting thevalve body on the member and pivotally mounting the torque tube adjacentthereto at said other end, said one end of the torque tube being fixedlyanchored by the anchoring means to the member, said torque tubeextending transversely between the fluid operated devices.
 13. Thecombination of claim 11 wherein said connecting means comprises a pairof operating lever arms.
 14. The combination of claim 13 includingbracket means fixedly mounting the valve body on one of the lever armsand pivotally mounting the torque tube adjacent thereto at said otherend, said one end of the torque tube being fixedly anchored by theanchoring means to the other of the lever arms.
 15. The combination ofclaim 1 wherein the load means includes a frame to which the fluidoperated devices are anchored, and a platform supported by the fluidoperated devices.
 16. The combination of claim 15 wherein said sensingmeans includes actuating means pivotally mounted on the frame andengageable with the valve for detecting movement of the platform. 17.The combination of claim 16 including additional valve mEansinterconnecting with the source of fluid through said first mentionedvalve means for detecting unequal displacement of the platform by thefluid operated devices.
 18. The combination of claim 17 including anelongated torque tube pivotally mounted by the frame at opposite ends,link means connecting the torque tube at said ends to the platform, thevalve element associated with said additional valve means beingengageable by the link means at one of said ends of the torque tube. 19.In combination, a frame, a load member movably mounted on the frame, aplurality of fluid operated devices anchored to the frame, meansinterconnecting the load member with the fluid operated devices atspaced locations, a source of fluid under pressure, directional controlmeans connecting the source to the fluid operated devices for impartingmovement to the load member in opposite directions, means connected tothe load member for sensing unequal movement of the fluid operateddevices during movement of the load member, valve means connected tosaid fluid operated device for differentially restricting flow betweenthe directional control means and the fluid operated devices in responseto engagement by the sensing means to compensate for said unequalloading, passage means connected to the valve means for conducting saidflow in opposite directions along different flow paths, andunidirectional flow blocking means responsive to said unequal movementof the fluid operated devices for conducting cross flow therebetweenalong selected ones of said flow paths.
 20. The combination of claim 19wherein said sensing means includes a torque tube connected to the loadmember, and actuating means displaceable by the torque tube intoengagement with the valve means.
 21. The combination of claim 19 whereinsaid valve means includes a valve body, a valve element displaceable bythe sensing means from a neutral position to compensating positionsblocking flow between the directional control means and one of the fluidoperated devices.
 22. In combination with a pair of fluid operateddevices, a source of working fluid and means for sensing unequal loadingof the fluid operated devices, a control valve assembly comprising avalve block having a pair of load ports connected to said fluid operateddevices and a supply port connected to said source, a single valveelement connected to the sensing means, means mounting the valve elementwithin the valve block for displacement from a neutral position by thesensing means to differentially restrict flow of the working fluidbetween the supply port and said pair of load ports, passage meansmounted within the valve block for conducting flow of the working fluidin opposite directions between the supply and load ports along separateand different flow paths, and pressure responsive check valve meansmounted in the passage means for unidirectionally conducting cross flowbetween said load ports in response to unequal loading of the fluidoperated devices.